Oil well cementing plug

ABSTRACT

This invention relates to an oil well cementing plug having a fluid relief passageway therethrough, such passageway containing a rod which maintains a fluid tight seal across said passageway until the rod is removed therefrom.

[451 Oct. 22, 1974 Morrisett et al.

166/155 166/154 Baker et a1. 166/154 2,560,901 7/1951 2,655,216 10/1953Baker et a1. 2,662,600 12/1953 Primary Examiner.1ames A. Leppink Okla.

Attorney, Agent, or Firm-John H. Tregoning [22] Filed: Apr. 23, 1971Appl. No.: 136,928

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p rgmmnmzzmm SHEET 10F 3 I NVENTORS O. L. Morrisefr Gail M. Boehm ATTORNZ \N \U T I. mt Q i w I M fi aQ N I i I m \N\\\\\ INVENTORS Gui! oehmQZ/ FIGURE 2. FIGURE 20. FIGURE 2b.

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ATTORNEY PATENTEDBCIZZIHM SIEET 3 [if 3 FIGURE illiliilrtlll M 1 41 111!!! INVENTORS O. L. Morriserr Gail M. Boehm ATTORN 1 on.WELL-CEMENTING PLUG BACKGROUND OF THE INVENTION It is common practice incementing long strings of casing to use a multiple stage cementing toolwhich contains two sliding sleeves, one above the other. The lowestsleeve is moved by dropping a plug from the surface onto a seat in thesleeve. A fluid tight seal is established at that point. Pump pressureacting across the plug pushes both the plug and sleeve downwardly ashort distance. When the upper sleeve is to be moved, a second plug isdropped from the surface onto a seat in the upper sleeve; as in thelower sleeve, a fluid tight seal is effected thereon. Pump pressurepushes the second plug and the upper sleeve downwardly.

As might be expected, as the second plug and upper sleeve start to movedownwardly, fluid trapped between the two plugs becomes compressed andexerts an upward force against the second plug. This force often buildsup to where it equals the pump pressure, making further downwardmovement difficult.

The present invention provides an oil well cementing plug whichcomprises an elongated housing having a fluid relief passagewaytherethrough, a rod slidably positioned in the passageway and retainingmeans for temporarily holding the rod in the passageway.

THE DRAWINGS An oil well cementing plug constructed in accordance withthe invention is illustrated in the accompa- DETAILED DESCRIPTIONReferring to FIG. 1, shown therein and generally designated by thereference character 11 is a cementing plug constructed inaccordance-with the invention. The plug 11 includes a. generallyU-shapedouter shell 12 which is constructed from an easily drillablematerial such as aluminum or cast iron. The desirability of using suchmaterial will be explained later. Upper end 13 of shell 12 contains aplurality of fins 14 to give stability to the plug when dropped into awell bore (not shown). Directly below fins 14, shell 12 forms an annularoutwardly projecting ring 15 which provides a downwardly and inwardlytapered surface 16. As will be shown later, surface 16 mates with acorresponding surface in a multiple stage cementing tool.

Lower end 18 of shell 12 contains passageway 19.

A number of recesses 20 are provided on inner wall 21 of shell 12. Theserecesses 20 provide an anchor for filler 22 which is packed into shell12 asshown in FIG. 1. Filler 22 can be composed of any number ofdrillable substances such as cement, rubber, or plastic. Preferrably, aplastic mixed with iron powder is used; this mixture adds weight to plug11 without being difficult to drill.

A sleeve 24 extends axially through the center of plug 11. Its lower end25 is positioned in aforementioned passageway 19 of shell 12 and isattached thereto via companion threads 26. Its upper end 27 terminateswithin the body of filler 22 but just below upper end 13 of shell 12.

A rod retainer 30 is attached to upper end 27 of sleeve 24 via companionthreads 31. Retainer 30 extends from sleeve 24 upwardly above upper end13 of shell 12. The upper portion of retainer 30 extending above plug11, designated at 32, contains two or more shear pins 34.

Sleeve 24 andretainer 30 cooperate to form a passageway, designated at35, extending from upper end 32 of retainer 30 downwardly throughretainer 30 and sleeve 24, emerging on the surface of shell 12 at lowerend 18.

An elongated rod 40 occupies passageway 35 as shown in FIG. 1.Previously mentioned shear pins 34 extend into apertures 42 on rod 40,holding the rod in the position shown. An O-ring 43, partly recessed inthe section of passageway 35 located in retainer 30, provides a fluidtight seal between retainer 30 and rod 40. The need for this sea] willbe shown below. The lower end of rod 40, designated at 44, is threadedto receive a nut 45. The body of nut 45 extends outwardlyperpendicularly to the axis of rod 40, and contacts lower end 18 ofshell 12. This arrangement prevents upward movement of rod 40 and theaccidental shearing of pins 34 by some force which could strike lowerend 44 of rod 40.

Rod 40 has three sectionsdesignated by the letters A, B, and C. SectionA includeslowerend 44 and the threaded portion adapted to receive nut45. Section B, extending upwardly through plug 11 and terminatingimmediately above upper end 32 of retainer 30, has a diameter slightlyless than that of passageway 35 through which rod 40 passes. Section Cis characterized by having a smaller diameter than has section B. Thereason for this is so that rod 40 need move downwardly only a shortdistance to remove the sealing effectof O-ring 43.

OPERATIONOF THE EMBODIMENT OF FIG. 1

FIGS. 2, 2a, and 2b illustrate the operation of the instant invention.In FIG. 2, casing 60, which is being cemented into well 61, containsmultiple stage cementing tool 62, shown schematically, which includeslower sleeve 63, covering ports 64, and upper sleeve 65. Sleeve 63includes an inwardly tapered surface 63a. Cementing plug 11, containingrod 40, has been dropped from the surface of the well and is freefalling downwardly through casing 60. A preceding stage of cement slurry66 has already been pumped down casing 60, out thereof and back up theannular space 67 to a point near tool 62.

FIG. 2a shows that plug 11 has landed in lower sleeve 63, surface 16lodging on surface 63a. Both sleeve 63 and plug 11 have been pumped downto rest on shoulder 68 in tool 62. Ports 64 have been opened by thisevent and another stage of cement slurry 69 is being pumped down casing60, through the ports and out into annular space 67. Slurry 69 cannotmove downwardly through tool 62 because rod 40 and aforementioned O-ring43 prevents flow through passageway 35 in plug 11, and also, a fluidtight seal is established between surface 16 of plug 11 and surface 63aof lower sleeve 63. A closing plug 70, following cement slurry 69, willland on upper sleeve 65 so that sleeve 65 can be moved down closingports 64, thus completing the cementing operation.

FIG. 2b illustrates the operational feature of the instant invention.Closing plug 70 has landed in upper sleeve 65 which now moves downacross ports 64; cement slurry 69 remaining within tool 62 is trappedand would begin to be compressed, except, before that can happen,closing plug 70 strikes rod 40 causing the shearing of pins 34 (FIG. 1)in plug 11. Rod 40, no longer retained, drops from plug 11 leavingpassageway 35 therein unobstructed so that cement slurry 69, otherwisetrapped, can escape therethrough. Upper sleeve 65 can now completelyclose without difficulty.

DESCRIPTION OF THE EMBODIMENT OF FIG. 3

FIG. 3 illustrates a second embodiment of the instant invention. Plug111 consists of a housing 112 having upper end 113 and lower end 114.Housing 112 is made from drillable material such as aluminum or castiron. An axial passageway 115 extends completely through housing 112 andconsists of three sections designated by the letters D, E, and F.Section D, extending upwardly from lower end 114, is the lowest section.Section E, the middle section, has a smaller diameter than does sectionD. Housing 112 contains two or more shear pins 116 which extend intosection E of passageway 115. Section F is the upper section and has asmaller diameter than does section E.

A U-shaped cap 117, having a plurality of holes collectively numbered118, is attached to lower end 114 of housing 112 via companion threads119. Positioned on housing 112 immediately above cap 117, is an annularresilient centralizer blade 120 and two annular cupshaped wiper blades121 and 122. Spaced above blade 122 and separated therefrom by a spacersleeve 123, is an annular outwardly projecting ring 124 having adownwardly and inwardly tapered surface 125 which mates with surface 63a(FIG. 2). Ring 124 is attached to housing 112 via companion threads 126.

A nut 127, having an outwardly projecting flange 128 is attached tohousing 112 above ring 124 via companion threads 129. A second annularcantralizer blade 130 is positioned on nut 127 between ring 124 andflange 128.

A rod, designated at 131 is initially partly positioned in passageway115 as shown in FIG. 3. Rod 131 consists of a short lower section 132and an elongated upper section 133. Lower section 132, containing anO-ring 134 and two apertures 135, has a diameter which substantiallycomplements that of section E of passageway 115. Aforementioned shearpins 116 extend into apertures 135, holding rod 131 in the positionshown. ring 134 provides a fluid tight seal between rod 131 and thewalls 136 of section E so that fluid cannot pass through passageway 115as long as rod 131 is retained by shear pins 116.

The diameter of the elongated upper section 133 of rod 131 is less thanthat of lower section 132 and may substantially complement that ofsecion F of passageway 115. The tolerance between section F and uppersection 133, however is not so close as to restrict movement of section133 therethrough.

OPERATION OF THE EMBODIMENT OF FIG. 3

In that the operation of cementing plug 111 is akin to that of plug 11(FIG. 1) described in detail above,

minor one, is that plug 111, when placed into well 61, must be pumpeddown casing 60 and into tool 62. This is so because blades 121 and 122,whose diameters exceed that of the internal diameter of casing 60, wipethe casing walls clean of residue cement and/or drilling mud (not shown)and push such matter ahead thereof.

The second feature relates to rod 131 in plug 111. As will be recalled,a cap 117 is attached to the lower end of plug 111. This cap confinesrod 131 within passageway after closing plug 67 (FIG. 2b) has struck therod and sheared pins 116. As is apparent from FIG. 4, after rod 131 hasdropped down to where it is resting on cap 117 and is mostly in sectionD of passageway 115, cement slurry 69, trapped in tool 62, will be ableto flow downwardly through the passageway, around rod 131, and out holes118 in cap 117. Retaining the rod within plug 111 is simply forconvenience in that it will be drilled up at the same time as the restof the plug. In fact, plug 111 can be constructed so that cap 117 has asingle center bore 118 large enough to permit rod 131 to drop out ofplug 111.

From time to time in the above descriptions, references have been madeto the materials used in constructing the present invention. Althoughthe cementing plugs can be structured so as to be retrievable from thesurface, it is much more desirable to simply drill them up into smallpieces and flush the pieces out of the well. For this reason, thematerial preferrably used for the rigid parts is aluminum, a materialexceptionally susceptible to the drill bit. Any number of rubbers,natural or man-made, can be used for the resilient parts as they too canbe drilled up easily; care being taken here in regart to chemicalreactions possible between such rubber and the slurry and/or otherfluids the rubber may contact.

The present invention has been described in a multiple stage cementingoperation. However, its use is not to be considered so limited. As theutility of the invention becomes better known and appreciated, more anddifferent uses will become apparent.

It will be apparent that many different embodiments of this invention,other than those described herein, may be made without departing fromthe spirit and scope thereof. Therefore, the instant invention is notintended to be limited except as indicated in the appended claims.

What is claimed is:

1. An oil well cementing plug, which comprises:

a. an elongated housing having a fluid pressure relief passagewaytherethrough;

b. a rod slidably and sealingly positioned in said passageway;

c. frangible retaining means between said rod and said housing andarranged to maintain said rod in a sealing relationship with saidhousing until said frangible retaining means are sheared; and

d. said rod adapted to move out of sealing contact with said housingupon shearing of said frangible retaining means.

2. The cementing plug of claim 1 wherein said housing includes an outershell and an inner filler.

3. The cementing plug of claim 2 wherein:

a. said outer shell is made from aluminum; and

b. said inner filler is made from epoxy resin and powdered lead.

4. The cementing plug of claim 3 wherein said inner filler is made fromepoxy plastic and ferrophosphorus.

5. A plug used in oil and gas well cementing operations, whichcomprises:

a. a hollow case having a plurality of fins at one end thereof;

b. a liner attached to and extending longitudinally through said case,said liner defining a fluid passageway;

c. a filler positioned in said case, said flller filling the spacebetween said case and said liner;

d. a rod slidably positioned in said fluid passageway, said rod havingat least one aperture positioned thereon; and

e. means for temporarily retaining said rod in said passageway.

6. The plug of claim 5 wherein said case is made from aluminum.

7. The plug of claim 5 wherein said case is made from cast iron.

8. The plug of claim 5 wherein said filler is made from plastic.

9. The plug of claim 5 wherein said means for retaining said rodincludes a member attached to one end of said liner, said member havinga bore extending axially therethrough and concentric with saidpassageway in said liner, said bore adapted to receive said rod, and atleast one shear pin extending laterally into said bore, said at leastone shear pin adapted to mate with said at least one aperture in saidrod.

10. A plug for use in oil well cementing operations, which comprises:

a. an elongated body having a passageway extending axially therethrough;

b. A U-shaped cap attached to the lower end of said body, said caphaving one or more bores extending therethrough;

c. a rod slidably and sealingly positioned in said passageway; and

d. frangible means for temporarily retaining said rod in saidpassageway.

11. The plug of claim wherein:

a. said body contains a plurality of resilient wiper blades disposedabout said body; and

b. said rod contains seal means thereon whereby said seal means incooperation with the walls of said passageway provide a fluid tight sealin said passageway.

12. The plug of claim 10 wherein one of said bores on said U-shaped capis adapted to pass said rod therethrough.

13. A plug for use in oil well drilling, cementing and testing toolswhere said tools contain inwardly projecting seats, said plugcomprising:

a. an elongated housing having an annular projection thereon, saidprojection adapted to engage the inwardly projecting seats in thedrilling, cementing and testing tools; said housing including an outershell and an'inner filler, said filler filling the space between saidshell and said liner;

b. a liner defining a passageway, said liner attached to and extendingaxially through said housing;

c; a rod slidably positioned in said passageway, said rod having atleast one aperture thereon; and,

d. means for temporarily retaining said rod in said passageway.

14. The plug of claim 13 wherein said outer shell is made from aluminumand said filler is made from epoxy plastic and powdered lead.

15. The plug of claim 13 wherein said means for temporarily retainingsaid rod in said passageway includes a member attached to one end ofsaid liner, said member having a bore extending axially therethroughadapted to receive said rod.

16. The plug of claim 15 wherein said member contains at least one shearpin extending laterally into said bore, said at least one shear pinadapted to mate with at least one aperture in said rod.

17. The plug of claim 16 wherein said member contains sealing means insaid bore whereby said sealing means, in cooperation with said rod,provides a fluid tight seal in said bore.

18. Plug apparatus for sealing off the internal bore of oil well casingand tubing and, when used with other plug apparatus, capable ofpreventing an hydraulic lock therebetween, comprising:

a. elongated external housing means containing a longitudinal axial boretherein;

b. an elongated fluid pressure relief means slidably and sealinglylocated within said axial bore in said housing and frangibly attached tosaid housing;

c. said pressure relief means extending out of said bore above saidhousing and adapted to be contacted from above by actuating plug meanswhereby said pressure relief means is moved out of sealing engagementwith said housing;

d. frangible shear means temporarily connecting said pressure reliefmeans to said housing means; and

e. first seal means located externally on said housing in annulararrangement adapted to sealingly engage the internal bore of the wallcasing or tubing.

19. The plug apparatus of claim 18 wherein said axial bore extendscompletely through said housing means and said pressure relief meanscomprises an elongated rod located in said axial bore and extendingcompletely therethrough, said rod containing second seal means thereon,and said axial bore in said housing means having an enlarged lowersection adapted to allow said second seal means to pass unrestricteddownward therethrough.

20. The plug apparatus of claim 19 wherein said elongated rod alsoextends out of the bottom of said bore in said housing means and saidplug apparatus further comprises upward travel preventing means fixedlyattached to the lower protruding end of said elongated rod; saidpreventing means adapted to abut the lower end of said housing meansthereby preventing upward movement of said rod in said housing means andpremature shearing of said frangible means.

21. The plug apparatus of claim 20 wherein said housing means furthercomprises an inner annular seal ing surface located within said axialbore above said enlarged lower section of said axial bore in saidhousing means; said inner annular sealing surface adapted to sealinglyengage said second seal means on said elongated rod. 1

22. The plug apparatus of claim 21 wherein said first seal meanscomprises an outwardly extending exterior annular shoulder attached tosaid housing means, said shoulder adapted to seat and sealingly engagein an internal annular seat in the well casing or tubing.

inner annular sealing surface above said enlarged lower section adaptedto sealingly engage said second seal means on said elongated rod.

24. The plug apparatus of claim 23 further comprising retaining meansfixedly attached to said housing means and located at the bottomthereof, said retaining means having one or more fluid passagestherethrough communicating with said bore passage; said retaining meansarranged to prevent said rod from sliding completely downward out ofsaid enlarged portion of said axial bore.

25. The plug apparatus of claim 24 wherein said first seal meanscomprises one or more outwardly extending elastomeric wiper elementsadapted to sealingly engage the internal bore of said tubing or casing.

26. The plug apparatus of claim 25 further comprising one or moreannular centralizing blades attached to said housing means, andoutwardly extending exterior annular valve seating means; said seatingmeans further comprising an annular ring having a downwardly andinwardly tapered seating surface located circumferentially thereon.

1. An oil well cementing plug, which comprises: a. an elongated housinghaving a fluid pressure relief passageway therethrough; b. a rodslidably and sealingly positioned in said passageway; c. frangibleretaining means between said rod and said housing and arranged tomaintain said rod in a sealing relationship with said housing until saidfrangible retaining means are sheared; and d. said rod adapted to moveout of sealing contact with said housing upon shearing of said frangibleretaining means.
 2. The cementing plug of claim 1 wherein said housingincludes an outer shell and an inner filler.
 3. The cementing plug ofclaim 2 wherein: a. said outer shell is made from aluminum; and b. saidinner filler is made from epoxy resin and powdered lead.
 4. Thecementing plug of claim 3 wherein said inner filler is made from epoxyplastic and ferrophosphorus.
 5. A plug used in oil and gas wellcementing operations, which comprises: a. a hollow case having aplurality of fins at one end thereof; b. a liner attached to andextending longitudinally through said case, said liner defining a fluidpassageway; c. a filler positioned in said case, said filler filling thespace between said case and said liner; d. a rod slidably positioned insaid fluid passageway, said rod having at least one aperture positionedthereon; and e. means for temporarily retaining said rod in saidpassageway.
 6. The plug of claim 5 wherein said case is made fromaluminum.
 7. The plug of claim 5 wherein said case is made from castiron.
 8. The plug of claim 5 wherein said filler is made from plastic.9. The plug of claim 5 wherein said means for retaining said rodincludes a member attached to one end of said liner, said member havinga bore extending axially therethrough and concentric with saidpassageway in said liner, said bore adapted to receive said rod, and atleast one shear pin extending laterally into said bore, said at leastone shear pin adapted to mate with said at least one aperture in saidrod.
 10. A plug for use in oil well cementing operations, whichcomprises: a. an elongated body having a passageway extending axiallytherethrough; b. A U-shaped cap attached to the lower end of said body,said cap having one or more bores extending therethrough; c. a rodslidably and sealingly positioned in said passageway; and d. frangiblemeans for temporarily retaining said rod in said passageway.
 11. Theplug of claim 10 wherein: a. said body contains a plurality of resilientwiper blades disposed about said body; and b. said rod contains sealmeans thereon whereby said seal means in cooperation with the walls ofsaid passageway provide a fluid tight seal in said passageway.
 12. Theplug of claim 10 wherein one of said bores on said U-shaped cap isadapted to pass said rod therethrough.
 13. A plug for use in oil welldrilling, cementing and testing tools where said tools contain inwardlyprojecting seats, said plug comprising: a. an elongated housing havingan annular projection thereon, said projection adapted to engage theinwardly projecting seats in the drilling, cementing and testing tools;said housing including an outer shell and an inner filler, said fillerfilling the space between said shell and said liner; b. a liner defininga passageway, said liner attached to and extending axially through saidhousing; c. a rod slidably positioned in said passageway, said rodhaving at least one aperture thereon; and, d. means for temporarilyretaining said rod in said passageway.
 14. The plug of claim 13 whereinsaid outer shell is made from aluminum and said filler is made fromepoxy plastic and powdered lead.
 15. The plug of claim 13 wherein saidmeans for temporarily retaining said rod in said passageway includes amember attached to one end of said liner, said member having a boreextending axially therethrough adapted to receive said rod.
 16. The plugof claim 15 wherein said member contains at least one shear pinextending laterally into said bore, said at least one shear pin adaptedto mate with at least one aperture in said rod.
 17. The plug of claim 16wherein said member contains sealing means in said bore whereby saidsealing means, in cooperation with said rod, provides a fluid tight sealin said bore.
 18. Plug apparatus for sealing off the internal bore ofoil well casing and tubing and, when used with other plug apparatus,capable of preventing an hydraulic lock therebetween, comprising: a.elongated external housing means containing a longitudinal axial boretherein; b. an elongated fluid pressure relief means slidably andsealingly located within said axial bore in said housing and frangiblyattached to said housing; c. said pressure relief means extending out ofsaid bore above said housing and adapted to be contacted from above byactuating plug means whereby said pressure relief means is moved out ofsealing engagement with said housing; d. frangible shear meanstemporarily connecting said pressure relief means to said housing means;and e. first seal means located externally on said housing in annulararrangement adapted to sealingly engage the internal bore of the wallcasing or tubing.
 19. The plug apparatus of claim 18 wherein said axialbore extends completely through said housing means and said pressurerelief means comprises an elongated rod located in said axial bore andextending completely therethrough, said rod containing second seal meansthereon, and said axial bore in said housing means having an enlargedlower section adapted to allow said second seal means to passunrestricted downward therethrough.
 20. The plug apparatus of claim 19wherein said elongated rod also extends out of the bottom of said borein said housing means and said plug apparatus further comprises upwardtravel preventing means fixedly attached to the lower protruding end ofsaid elongated rod; said preventing means adapted to abut the lower endof said housing means thereby preventing upward movement of said rod insaid housing means and premature shearing of said frangible means. 21.The plug apparatus of claim 20 wherein said housing means furthercomprises an inner annular sealing surface located within said axialbore above said enlarged lower section of said axial bore in saidhousing means; said inner annular sealing surface adapted to sealinglyengage said second seal means on said elongated rod.
 22. The plugapparatus of claim 21 wherein said first seal means comprises anoutwardly extending exterior annular shoulder attached to said housingmeans, said shoulder adapted to seat and sealingly engage in an internalannular seat in the well casing or tubing.
 23. The plug apparatus ofclaim 18 wherein said axial bore extends completely through said housingmeans and said pressure relief means comprises an elongated rod locatedpartially within said axial bore and extending above said housing means;said rod containing second seal means around the lower end thereof; andsaid axial bore in said housing means having an enlarged lower sectionadapted to allow said second seal means to pass unrestricted downwardtherethrough and an inner annular sealing surface above said enlargedlower section adapted to sealingly engage said second seal means on saidelongated rod.
 24. The plug apparatus of claim 23 further comprisingretaining means fixedly attached to said housing means and located atthe bottom thereof, said retaining means having one or more fluidpassages therethrough communicating with said bore passage; saidretaining means arranged to prevent said rod from sliding completelydownward out of said enlarged portion of said axial bore.
 25. The plugapparatus of claim 24 wherein said first seal means comprises one ormore outwardly extending elastomeric wiper elements adapted to sealinglyengage the internal bore of said tubing or casing.
 26. The plugapparatus of claim 25 further comprising one or more annularcentralizing blades attached to said housing means, and outwardlyextending exterior annular valve seating means; said seating meansfurther comprising an annular ring having a downwardly and inwardlytapered seating surface located circumferentially thereon.